Power poles in the burned out Powerhouse Fire area along San Francisquito Canyon Road in Green Valley. (Photo by Hans Gutknecht/Los Angeles Daily News)

Los Angeles Department of Water and Power crews re-energized a tripped circuit twice in the area where the 2013 Powerhouse Fire started in the hour before flames raced across the hillside, according to a U.S. Forest Service investigation report released this week.

One DWP employee also told investigators about an incident on the same circuit’s power line a few months earlier that caused a building fire.

The Camp Service Line, inspected by the Forest Service, showed signs of “arcing” — a phenomenon in which current jumps from one line to another and discharges electricity, almost like lightening — according to the report. State regulations require utilities to design and maintain power lines with enough spacing to prevent that from happening.

Firefighters who arrived on scene saw the Camp Service line swaying in high winds, the report says. The power line serves the city’s first hydroelectric power plant, north of Castaic Lake.

Plaintiffs in a suit over the fire allege neglected equipment caused the Powerhouse blaze, which burned 24 homes and more than 30,000 acres near Santa Clarita and in the Angeles National Forest. Last month, the Forest Service announced that power lines caused the blaze.

DWP officials say they have cooperated with investigators and are waiting for experts to inspect some equipment. Employees told the Forest Service they followed normal procedures after the circuit first tripped the day of the Powerhouse and that everything appeared ordinary. None of the power lines fell to the ground, so it was unlikely that the lines could have generated enough of a spark to start a ground fire, DWP officials said in a statement.

“We are deeply concerned for those residents who lost homes and property and understand that they want closure,” DWP General Manager Marcie Edwards said in the statement. “If it is determined that our equipment was involved in the start of the fire, we will evaluate the damage claims accordingly.”

The statement says the cause of the trips could have been “ash and soot causing an interruption in the flow of electricity over the lines.” But DWP employees interviewed by the Forest Service said they saw smoke before, not after, the two trips.

One of the screws used to hold the power line to a pole was stripped of its thread, investigators found. The department has struggled to keep up with maintenance of its power system, and city officials have requested DWP managers devise a plan to catch up.

While many DWP power poles have exceeded their 60-year lifespan, department officials said this week they replaced the power poles and equipment in question in 2008. Public records show some wooden poles in the vicinity were more than 80 years old at the time of the fire, but DWP spokesman Joe Ramallo says they were not the ones under investigation and they have since been replaced.